The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Additive manufacturing devices produce three-dimensional parts by sequentially adding materials in a pattern. Some classes of additive manufacturing devices produce polymer parts solidified from a photopolymer resin which has been exposed in a layer-wise fashion to electromagnetic radiation generated by a light source such as a projector. The light source projects a cross sectional image into a build area, solidifying a layer of photopolymer resin into a hardened layer, thereby adding another layer to the object being formed. In order to create parts with a high degree of detail and accuracy, removing the hardened layer from the build area without deforming, destroying, or otherwise damaging the layer or other portions of the part is essential.
When the layer is formed, the newly-formed layer often adheres to an image surface found in the build area. Two types of forces prevent separation at the interface between the image surface and the newly-formed layer: (1) the adhesion force between the image surface and the newly-formed layer; and (2) a vacuum force present between planar objects in a fluid. The adhesion force is comprised of chemical bonding forces between the image surface and the newly-forced layer. In some embodiments, the adhesion force also comprises mechanical adhesion forces between the image surface and the newly-formed layer. In order to separate the part from the image surface and continue assembling it, a separation force must be applied in order to overcome the adhesion and vacuum forces present. Application of the separation force stretches and strains the part being formed in non-uniform, undesirable ways. In some cases, the separation force is strong enough to distort or destroy fragile portions of a part because the fragile portion is stretched, strained, and even completely separated from the part as the part is repositioned to form the next layer of the part. Because this separation force destroys or damages fine detailing in a desired part design, resolution has been limited. Parts containing, for example, very thin segments or intricate detailing (e.g. channels, tubing, etc.) cannot be produced, are produced with an extremely high failure rate, or must be produced at a very slow rate using different photopolymers in order to produce a part containing fragile sections that will not deform when exposed to the separation forces.
Some additive manufacturing devices utilize a thin film as the build surface or image surface. Such films include Teflon® films (available from Du Pont Co. of Wilmington, Del.) or other non-stick materials. The film may also be a flexible polyurethane or other material. Such devices struggle to ensure a uniform distribution of material to create subsequent layers during the build process.
Given the foregoing, what is needed are devices, systems and methods which facilitate creating a part via additive manufacturing wherein separation forces are reduced. Furthermore, providing a constant, uniform layer of photopolymer resin to form subsequent layers from is desired.